


In the Blink of an Eye

by Balloon_ROYALTY



Category: Undertale (Video Game)
Genre: And also a mistake, Marriage, Oneshot, This is completely sfw, Waterfall (Undertale), reader is a monster
Language: English
Status: Completed
Published: 2021-03-19
Updated: 2021-03-19
Packaged: 2021-03-28 04:02:09
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,821
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30133707
Author URL: https://archiveofourown.org/users/Balloon_ROYALTY/pseuds/Balloon_ROYALTY
Summary: *I apologize.*Onionsan deserved better fics.*That said, I didn't check for errors because I couldn't stand rereading it.
Relationships: Onionsan (Undertale)/Reader
Comments: 1
Kudos: 2





	In the Blink of an Eye

You had never had much in common with the others.  
Waterfall was growing claustrophobic- you weren't the biggest monster, but even you could tell as much. Those who weren't primarily constrained to the water were _lucky_ \- they could go wherever they wished.

But not you.

You'd seldom left your pond for fear of drying out. In fact, it was only that very threat that drove you away from it in the end.

Your home was drying up. You had no choice.

And so you'd moved, feeling all-too-sorry for yourself as you dragged yourself from one pond to where you'd been told the next might be. You'd asked for help.

But nobody came.

Nobody ever came. You were used to being alone, you thought, as you finally allowed yourself to fall into the cool water of the small lake you'd finally come to.

Exhausted, you closed your eyes, letting precious water fill your gills as you rested.

Nobody was ever there for you...

... Which is why you were so shocked upon waking a mere hour later, a massive shadow looming over you. Could it be- was there another aquatic monster in here? You cautiously swam out from underneath their mass.

... They were staring down at you.

"Hey... there..." They spoke softly, their breath bated. As if they hadn't spoken to a single soul in months.

"I'm Onionsan! Onionsan, y'hear!"

You couldn't help but give a brief chuckle, wondering for a moment if they'd named themself.

"Have you got a name? It's alright if you don't... I get it..."

... You guessed that confirmed your suspicions. You nodded. "Yeah. My name's [Y/N]. It's nice to meet you, uh. Onionsan." You tried not to grin.

"... So... what brings you here!" Onionsan spoke after a moment of tense silence, their eyes wide but their grin widened. They gave a nervous laugh. "Are you... visiting? It's okay if you are, y'hear! Even if I'm..." They hesitated. "A little lonely..."

You paused, the reality of your situation washing back over you with an icy chill.

"... No, I... my home's dried up." You admitted, your words nearly catching in your throat. "I had no choice. I uh. I hope you don't mind neighbors?"

You'd apparently said the right thing, because Onionsan's eyes soon began to shine. "Of COURSE I don't mind! It's, kind of more like roomies, isn't it? I got so much to talk about, y'hear! It's been so long since I got to live _with_ someone..."

And so you began to talk. Onionsan showed you where the food was stored, and you told Onionsan about what life outside of this tiny lake was like.

Or, as much as you could tell them, considering you'd been in an even tinier pond for the majority of your life.

Onionsan told you about their musical ambitions, and you told Onionsan about your family who had moved to aquariums in the city. That seemed to sober them up a bit. They paused.

"... Why didn't you go? I mean, it's crowded... it would have been awful. But you would have been with your family, y'hear!"

"I was... uh. I was actually too late." You admitted. "They were the last ones allowed in before the Aquarium was completely full."

Though you'd known Onionsan for almost a week at that point, you were still surprised to be suddenly embraced in a gentle hug.

Their tentacles wound securely around your middle.

Living so close together-- it was almost like boundaries broke down altogether between the two of you. Perhaps sooner than they should have, but you weren't uncomfortable with it at all.

More importantly, you hadn't realized how... upset you still were about your family.

"... You should call them, y'hear! I bet they'd love to hear from you."

You rolled your eyes. "Yeah, I guess I could introduce you..."

* * *

The day the barrier broke was a shock to the both of you. One moment you were engulfed in a flash of light, the next--   
... Well, you weren't entirely sure what happened. But you knew a few things for sure.

You knew the barrier was broken.   
You knew you had Frisk to thank.   
You knew you would be free soon.

"I'll finally be in the ocean, y'hear!" Onionsan was the picture of excitement, their tentacles propping up their awe-inspiringly massive head as they sighed.

"And... and that means... you'll finally be able to see your family, y'hear..."

The realization hit you like a truck.

"... And... go without me, y'hear. You don't need to apologize... I know it'll take longer for me to get out-"

"No-!" You insisted, yelling it before you had time to even think. You grasped onto one of Onionsan's tentacles, holding that small part of them close to your heart.

"I mean... no, Onionsan. We're friends, after all. And you've spent way more time with me than my dumb family has, anyway."

"... Aw, shucks." Onionsan sniffed, wiping a tear from their eye.

"I'll wait with you. As long as it takes." You promised.

* * *

The next few months were a blur. Deciding what to keep and what to throw away, waiting patiently for the day other monsters came to help Onionsan up through the mountain, past the Core... onto the surface...

There were so many things you'd never seen before. A part of you regretted never exploring the Underground before. The rational side of you told you that it would have been impossible.

There was no point worrying about it now anyway. You were about to experience more freedom than you ever had before- so much that you didn't even know what you'd do first.

"Can you believe we're finally here? It felt like we'd never get here, y'hear!"

Something warm bloomed in your chest. You nodded, feeling unable to speak as the tank was abruptly drained into the ocean.

You gasped.

The salty seawater was unlike anything you'd ever breathed underground. It was so... fresh, so clean.

Onionsan was still going on and on, but you abruptly realized something before they finished talking.

"... Hey, Onionsan?" You interjected. "I've got something I need to do. I'll be back soon." You told them, pulling out your phone.

Onionsan faltered, seeming crushed. But they didn't try to stop you.

"I... aw... alright, I know. I see... well, you'll be back, right? I'll see you soon, y'hear!"

You grinned back. "Of course, y'hear!"

* * *

Visiting your family wasn't worth it. What kind of family would leave their child alone in Waterfall, anyway?   
You should have known this was a bad idea. You'd just... you'd hoped they'd changed.

They weren't cruel as much as they were uncaring- they spoke as if they didn't know you.

They acted like they were strangers in your parents' and siblings' skin.

They weren't what you thought about when you thought of family anymore. Your heart tightened as you laid back on the bed in your parents' spare room.

To you... family meant...   
Family meant one person. One person who'd always been there for you. One person who had been patient for you, who hadn't tried to leave for the aquarium even when a vacancy DID open.

...

"... Sorry, Onionsan..." You mumbled to yourself, draping an arm over your eyes.

You had to go home.

* * *

"ONIONSAN!" You didn't realized how thrilled you were to see them again until you finally saw the back of their big round head. Your limbs pumped faster as they turned around, propelling you through the open sea and directly into their waiting tentacles.

"[Y- Y/N]!" They gasped, seeming shocked at the sight- and impact- of you. Their tentacles gently began to wind around you. "I thought... you'd wanna spend more time with your family, y'hear..."

You shook your head, grimacing.

"... I don't want to talk about it. But... hey, I thought..."

Onionsan raised an eyebrow.

"Nevermind." You said hurriedly, feeling your cheeks heat up. "Nevermind that, I mean. But what if we... made a proper house? That you could fit in? The ocean's definitely big enough, right?"

"That sounds- that sounds amazing, y'hear! I never woulda even thought of it..." Onionsan sniffed, their lower lip quivering.

"Alright!" You insisted, rolling up your figurative sleeves. (Loose sleeves weren't the best for swimming.) "It's not gonna get done if we don't get started, right?"

* * *

Your house had been finished for days before you had the courage to ask, finding yourself tripping over your words at every moment before this.

But not this time.

This time, you were ready.

"... Onionsan?" You mumbled, pausing. "I know I didn't... tell you the whole story about what happened with, um. My parents."

Onionsan perked up, clearly attentive.

"You wanna talk about it, y'hear?"

"... When I thought about family, I only, um. I only thought of... you. There was nothing for me there anymore."

Onionsan's eyes glistened as they took in your words. With tears or hope, you weren't sure.

"That's why, I. I know this is kind of a sudden question but, I."

Your throat tightened. But you couldn't stop now.

"... Did you want to start a family with me?"

Onionsan began openly sobbing into their tentacles. For a moment, you worried you'd said something wrong.

" _I- I- I'd love to, [Y/N]!_ "

* * *

The next few months were like a dream. You planned out your wedding meticulously, but the day of the event still caught you by surprise. Onionsan, when acquiring your wedding ring, had forgotten to ask for a ring not sized to their own tentacles. The ring ended up being big enough to use as a belt, and you gladly did so, donning it proudly at the head of the aisle.

There weren't many monsters there, granted. You'd invited your family out of formality, and Onionsan had invited some old band members they were hoping to make some new tunes with. But it didn't have to be a big event to be the perfect start to your new life.

It was small and cozy. Just like everything you'd wanted.

~~~

"... Back when we were in the underground..." You reflected, watching Onionsan play with your child of two months. Onionsan had carried the child- you had been worried at first, but they assured you the size difference was safer for them than it was for you.

"You know, I thought I wanted to have the whole sea to myself. More than anything." Onionsan nodded emphatically.   
"... But I don't mind being cooped up with you." You continued, leaning up to press a kiss to their massive cheek. "You make me want to stay put. Right here."

Onionsan caressed your cheek with a tentacle, obviously flustered as you kept talking anyway.   
"... I love you so, so much. This makes all the waiting I did worth it, you know." You wound your arms around a couple of their tentacles.

Onionsan giggled, finally nuzzling back against you.

"Aw. You're gonna burst my ego, y'hear."

They paused, their entire orblike head lighting up pink.

"I... I love you too."

**Author's Note:**

> *AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAA


End file.
